# File lib/phusion_passenger/platform_info/apache.rb, line 123
        def self.apu_config
                if env_defined?('APU_CONFIG')
                        return ENV['APU_CONFIG']
                elsif apxs2.nil?
                        return nil
                else
                        filename = `#{apxs2} -q APU_CONFIG 2>/dev/null`.strip
                        if filename.empty?
                                apu_bindir = `#{apxs2} -q APU_BINDIR 2>/dev/null`.strip
                                if apu_bindir.empty?
                                        return nil
                                else
                                        return select_executable(apu_bindir,
                                                "apu-1-config", "apu-config")
                                end
                        elsif File.exist?(filename)
                                return filename
                        else
                                return nil
                        end
                end
        end